This project is concerned with the development of the retina. It will exploit the ability of the retinal rudiment of the frog embryo to be grown in tissue culture and will utilize various inhibitors, microsurgery and microinjection techniques as well as light and electron microscopy in evaluating the developmental mechanisms which control retinal differentiation. The project consists of three parts (1) The retinal rudiment in the frog embryo contains pigment granules produced during the development of the egg. The retina eliminates this egg pigment long before other parts of the embryo are free of this pigment. A portion of this study will be directed toward determining what component of the granule the retinal cells recognize and how the pigment granules are transported within the neuroepithelial cells to the site of their elimination. (2) The interactions between the retina and pigment epithelium in the adult are well known. A portion of this study will be directed at determining the necessity of the pigment epithelium for the differentiation of the photoreceptors. (3) The lineage of retinal cells will be studied by following the progeny of single cells in the retinal neuroepithelium and determining how they differentiate.